CSE333 Exercise 3

Out:   Friday, April 10
Due:   Wednesday, April 15 by 11 am PST
Rating:   2 (note)
CSE 333 Exercise Rating Scale

Each exercise this quarter is rated on a integer scale of 1 – 5, inclusive, with 1 being the "least time-consuming" and 5 being the "most time-consuming".

This difficulty scale is meant as a rough guide for you in predicting the amount of time to set aside for each exercise as you balance the work required for 333 with your other obligations. However, it is necessarily imperfect as everyone's set of circumstances and experiences with the exercises differ. If your experience with an exercise does not align with its rating, that is not a reflection of you or your abilities.

Goals

  • Define and use structs with typedef.
  • Use malloc and free to manage dynamically-allocated data without memory leaks.
  • Write some basic automated tests in C.
  • Modularize a C program across multiple files.

Problem Description

Your job is to write a C program that does the following:

  • Uses typedef to define a new structured type called Point3d, which contains int32_t fields for x, y, and z coordinates.
    • This means you should be able to refer to the struct with the following syntax: Point3d p = ...;
    • For the sake of the autograder, do not use typedef to define pointers to Point3d structs to be Point3dPtr; instead, use Point3d*.
  • Defines a function called Point3d_Allocate that (1) accepts three int32_t arguments, (2) malloc's space for a Point3d, (3) assigns the three arguments to the x, y, and z fields, and (4) returns (a pointer to) the malloc'ed Point3d.
  • Defines a function called Point3d_Scale that (1) accepts one Point3d* and one int32_t value as arguments, (2) scales the x, y, and z fields of the pointed-to struct by the given value, and (3) returns nothing.
    • For the sake of the autograder, do not return a bool, even though it would a reasonable design decision to do so.
  • Defines a function called Point3d_GetOrigin that (1) accepts no arguments, (2) constructs a Point3d with x, y, and z equal to zero, and (3) returns a copy of the struct.
  • Has a main function that runs at least one automated test on each of your functions. Make sure to read the relevant portion of the Implementation Notes below ("Testing") very carefully to make sure that you understand what this is asking for.
  • Is modularized nicely across three files: Point3d.h, Point3d.c, and ex3.c.
    • Point3d.h should contain the struct definition and function declarations related to Point3d.
    • Point3d.c should contain the function definitions.
    • ex3.c should contain the main that tests your functions.

Implementation Notes

Error Handling & Robustness

As part of this exercise, you will have to make design decisions about how to handle errors. Be sure to take some time and reason about what arguments might be problematic for each function. Be sure to handle other types of errors, like the case in which malloc fails. Whatever decisions you make, be sure to document them appropriately.

  • You may ignore any possible integer overflow errors.

Memory Cleanup

Make sure your main frees any memory that was dynamically allocated, even when handling edge cases. We will be using valgrind (valgrind --leak-check=full ./ex3) to check for memory leaks and other memory issues.

Testing

For the purposes of this exercise, it is enough for you to write code that makes use of all of the functions that you wrote and verifies that the struct members contain the correct values at each step. When an error is encountered during testing, you should immediately return an appropriate status code to indicate failure in addition to printing an error message. This signals an error to the parent process (this is what makes it automated) and is easier to detect than having to manually scan over your program output, especially if you have a lot of tests.

  • main is considered testing code for your Point3d module. Testing code is the only place where the use of assert() is allowed, though you do not need to use it at all if you don't want to.

Style Focus

General

For the sake of our autograder, make sure that your function and type names match the specifications exactly, including capitalization. You should write comments explaining the behaviour and purpose of the struct and functions you define. Be sure that the comments you write document how errors are handled.

Typedef

This is supposed to make your life easier! Make sure that your syntax is correct and that you're taking advantage of the new alias.

Multiple files

Make sure to include header guards, where appropriate, and that you place the function block comments in the appropriate place.

Submission

Submit the following file(s) by creating an ex3-submit tag in your exercise repo before the assignment deadline. The file(s) should be located in the exact directory listed below (there should be a folder titled ex3 with the ex3.c, Point3d.h, and Point3d.c files within that folder), including capitalization:

  • ex3/ex3.c
  • ex3/Point3d.h
  • ex3/Point3d.c

For full credit, your code must:

  • Compile without errors or warnings on CSE Linux machines (lab workstations, attu, or CSE home VM).
  • Have no runtime errors, memory leaks, or memory errors (gcc and valgrind).
  • Be contained in the three files described above that compile into an executable with the following commands: 
    $ gcc -Wall -g -std=c17 -c -o Point3d.o Point3d.c
$ gcc -Wall -g -std=c17 -c -o ex3.o ex3.c
$ gcc -Wall -g -std=c17 -o ex3 ex3.o Point3d.o
  • Have a comment at the top of your .c file with your name(s) and CSE or UW email address(es).
  • Be pretty: the formatting, modularization, variable and function names, commenting, and so on should be consistent with class style guidelines. Additionally, the linter shouldn't have any complaints about your code (cpplint.py --clint).
  • Be robust: your code should deal with hard-to-handle/edge cases and bogus user input (if there are any) gracefully.